1. Field of the Invention
This invention relates to a high frequency module device and a method for producing the device. More particularly, it relates to a high frequency module device loaded in a variety of electronic equipment, such as personal computers, a portable telephone set or audio equipment to form an ultra-small-sized communication function module having e.g., an information communication function or an information storage function.
2. Description of Related Art
The information of various sorts, such as music, speech or pictures, has come to be handled readily by a personal computer or a mobile computer in recent years with the advent of data digitizing technique. Moreover, the above information may be compressed in bands by speech codec or picture codec techniques and has come to be distributed readily and efficiently to a variety of communication terminal equipment by digital communication or digital broadcast. For example, the audio video data (AV data) can be received outdoors by portable telephone sets.
Meanwhile, as a network system convenient for a small territory, including homes, has now been proposed, variable utilization of transmission/reception systems for e.g., data has become possible. As such network system, a variety of next-generation wireless systems, such as a narrow band radio communication system of the 5 GHz band, as proposed in IEEE 802.1a, radio LAN system of 2.45 band, as proposed in IEEE 802.1b, or the short range radio communication system, termed Bluetooth, are stirring up notice. In a transmission/reception system for e.g., data, such wireless network systems are effectively utilized to exchange a variety of data, to access the Internet or to transmit/receive data in households or outdoors in a handy manner without using e.g., relaying devices.
Meanwhile, in a communication terminal equipment, it is necessary to modulate/demodulate analog high frequency signals in the transmission/reception unit. So, a high frequency transmission/reception circuit 100 of a superheterodyne system, in which the transmission/reception signals are first converted into signals of an intermediate frequency, as shown in FIG. 1, is routinely used.
A high frequency transmission/reception circuit 100 includes an antenna unit 101 provided with an antenna or with a changeover switch for transmitting or receiving information signals, and a transmission/reception switching unit 102 for switching between transmission and reception. The high frequency transmission/reception circuit 100 also includes a receipt circuit unit 105 made up e.g., of a frequency conversion circuit unit 103 or with a demodulation circuit unit 104. The high frequency transmission/reception circuit 100 also includes a transmission circuit unit 109 made up e.g., of a power amplifier 106, a driving amplifier 107 and a modulation circuit unit 108. The high frequency transmission/reception circuit 100 also includes a reference frequency generating circuit for supplying a reference frequency to the receipt circuit unit 105 or to the transmission circuit unit 109.
The high frequency transmission/reception circuit 100 has an extremely large number of component parts, such as large-sized functional components, interposed between respective stages, such as a variety of filters, local oscillators (VCO) or SAW filters, or passive components, such as inductors, resistors or capacitors, proper to the high frequency analog circuits, such as matching circuits or bias circuits. With the high frequency transmission/reception circuit 100, each circuit part is designed as an IC, however, the filter interposed between the respective stages cannot be built into the IC. Moreover, a matching circuit is necessary to provide as an exterior type circuit. Thus, the high frequency transmission/reception circuit 100 is generally bulky in size to present obstacles in reducing the size and weight of the communication terminal equipment.
On the other hand, a high frequency transmission/reception circuit 110 of the direct conversion system, designed to transmit/receive information signals without conversion into an intermediate frequency, as shown in FIG. 2, is also used in the communication terminal equipment. In this high frequency transmission/reception circuit 110, information signals, generated in a source, are directly modulated in a modulation circuit unit 114 to the preset frequency range, without conversion to the intermediate frequency, and transmitted over an antenna 111 through an amplifier 115 and a transmission/reception switching unit 112.
In such high frequency transmission/reception circuit 110, in which the information signals are transmitted/received by direct detection without conversion of the intermediate frequency of the information signals, the number of component parts, such as filters, is reduced to simplify the overall structure so that expectation may be made of a structure closer to a one-chip structure. However, in the high frequency transmission/reception circuit 110, the filters or matching circuits, arranged on the downstream side, need to be coped with. Moreover, with the high frequency transmission/reception circuit 110, in which the information signals are amplified once and for all in the high frequency stage, it becomes difficult to realize a sufficient gain such that it is necessary to perform amplification in the baseband portion. Thus, the high frequency transmission/reception circuit 110 is in need of a DC offset cancelling circuit or a redundant low-pass filter, while the overall power consumption is increased.
In the conventional high frequency transmission/reception circuit, requirements for reduction in size or weight of the communication terminal equipment cannot be met satisfactorily for the superheterodyne system or the direct conversion system. For this reason, a variety of attempts have been made in designing the high frequency transmission/reception circuit as a small-sized module by a simplified structure based on e.g., a Si-CMOS circuit. That is, one of the attempts is to form an active device of high properties on an Si substrate and to build filter circuits or resonators on an LSI as well as to form the logic LSI of the baseband portion as an integrated circuit to produce a so-called one-chip high frequency transmission/reception module.
However, in such high frequency transmission/reception module, how an inductor of high performance is to be formed on an LSI is crucial. In a high frequency transmission/reception circuit 120, a large-sized recess 124 is formed in register with an inductor forming site 123 of an Si substrate 121 and an SiO2 insulating layer 122, as shown in FIG. 3. In the high frequency transmission/reception circuit 120, a first wiring layer 125 is formed facing the recess 124, while a second wiring layer 126 closing the recess 124 is formed to form an inductor 127. In another type of the high frequency transmission/reception module, the wiring pattern is segmented and raised from the substrate surface to float in air to form an inductor. However, in such high frequency transmission/reception module, the process of forming the inductor is extremely labor-consuming such that the production cost is raised due to the increased number of process steps.
On the other hand, in a one-chip high frequency transmission/reception module, electrical interference of an Si substrate interposed between the high frequency circuit portion of an analog circuit and a baseband circuit portion of a digital circuit poses a serious problem. As for the high frequency transmission/reception module, an Si substrate high frequency transmission/reception module 130 shown in FIG. 4 or a glass substrate high frequency transmission/reception module 140 shown in FIG. 5 has been proposed. In the high frequency transmission/reception module 130, an SiO2 layer 132 is formed on an Si substrate, after which a passive elements forming layer 133 is formed by a lithographic technique.
In the passive elements forming layer 133, there are formed passive elements, such as inductors, resistors or capacitors to a multi-layer structure by a thin film forming technique or by a thick film forming technique, along with a wiring pattern, although details are not shown. In the high frequency transmission/reception module 130, a terminal unit connected to an internal wiring pattern is formed on the passive elements forming layer 133 through e.g., a via-hole (relaying through-hole) and a circuit device 134, such as a high frequency IC or LSI, is directly mounted on the passive elements forming layer 133 by e.g., a flip-chip mounting method.
The high frequency transmission/reception module 130 may be mounted on e.g., a motherboard to isolate the high frequency circuit portion and the baseband circuit portion from each other to suppress electrical interference therebetween. Meanwhile, in such high frequency transmission/reception module 130, there is presented a problem that the electrically conductive Si substrate 131, operating when forming each passive elements in the passive elements forming layer 133, is obstructive for optimum high frequency characteristics of the respective passive elements.
In a high frequency transmission/reception module 140, a glass substrate 141 is used as a base substrate to overcome the aforementioned problem concerning the Si substrate 131 of the frequency transmission/reception module 130. In the high frequency transmission/reception module 140, a passive elements forming layer 142 is similarly formed on the glass substrate 141 by the lithographic technique. In the passive elements forming layer 142, there are formed passive elements, such as inductors, resistors or capacitors by a thin film forming technique or by a thick film forming technique, to form a multi-layer structure, along with a wiring pattern, although not shown in detail. In the high frequency transmission/reception module 140, a terminal unit connected to an internal wiring pattern is formed on the passive elements forming layer 142, through e.g., a via-hole (relaying through-hole), and a circuit device 133, such as a high frequency IC or LSI, is directly mounted on the passive elements forming layer 133 by e.g., a flip-chip mounting method.
In the high frequency transmission/reception module 140, employing an electrically non-conductive glass substrate 141, the degree of capacitative coupling across the glass substrate 141 and the passive elements forming layer 142 can be suppressed to form a passive elements exhibiting superior high frequency characteristics within the passive elements forming layer 142. However, in mounting the high frequency transmission/reception module 140 on e.g., a motherboard, a terminal pattern is formed on a surface of the passive elements forming layer 142, as shown at 150, and the high frequency transmission/reception module 140 then is mounted, such as by wire bonding, to a mother board 151, after which it is connected to the motherboard. So, with the high frequency transmission/reception module 140, a terminal pattern forming step and a wire-bonding step are necessitated.
In the above-described high frequency transmission/reception module, a highly precise passive elements forming layer is formed on the base substrate, as described above. In forming the passive elements forming layer on the base substrate by a thin film forming technique, the base substrate is required to exhibit thermal resistance against rise in the surface temperature at the time of sputtering, retention of depth of focus at the time of lithography and contact alignment characteristics at the time of masking. So, the base substrate is required to exhibit high planarity, insulating properties, thermal resistance properties and resistance against chemicals.
The Si substrate 131 and the glass substrate 141 exhibit these properties to enable passive elements of low cost and low loss by a process different from the LSI process. Moreover, as compared to the pattern forming method by printing, as used in a conventional ceramic module technique or to the wet etching method used in forming a wiring pattern on a printed wiring board, the Si substrate 131 and the glass substrate 141 permit passive elements to be formed thereon to a high precision, while permitting the device size to be reduced to approximately one-hundredth of that achieved with the above-mentioned conventional methods. In addition, with the Si substrate 131 and the glass substrate 141, the marginal usable frequency band of the passive elements can be raised to 200 GHz by comminution.
However, in the above-described high frequency transmission/reception module, high frequency signal pattern formation, wiring to supply the power source or the grounding or the wiring of the control signals are made through a wiring layer formed on the Si substrate 131 or on the glass substrate 141. In the high frequency transmission/reception module, electrical interference is produced across respective wirings, while the problem of cost due to forming the wiring layer as a multi-layer wiring is also raised.
Moreover, the high frequency transmission/reception modules 130, 140 are packaged as shown in FIG. 6. On one major surface of an interposer substrate 151 of a package 150 is mounted a high frequency transmission/reception module 130, with the entire assembly being encapsulated in an insulating resin 156. On the front and reverse surfaces of the interposer substrate 151 are formed pattern wiring layers 152, 153, respectively. Around the loading area for the high frequency transmission/reception module 130 are formed numerous lands 154.
As the high frequency transmission/reception module 130 is loaded on the interposer substrate 151 of the package 150, this high frequency transmission/reception module 130 and the lands 154 are electrically connected together by wire bonding 155 to enable power supply or signal transmission/reception. So, there is formed, on a surface layer of the high frequency transmission/reception module 130, having mounted thereon a high frequency IC 134 or a chip component 135, a wiring pattern 136 interconnecting these mounted components and connection terminals 137 to the wire bonding 155. The high frequency transmission/reception module 140 is also packaged in a similar manner.
Since the high frequency transmission/reception modules 130, 140 are packaged through the interposer substrate 151 as described above, there are presented problems that the package 150 is increased in thickness or size, while the cost of the package is raised.
In the Si substrate or in the glass substrate high frequency transmission/reception module, a shield cover is provided for overlying the high frequency IC or circuit devices, such as LSIs. However, there is raised a problem that the module becomes bulky depending on the heat radiating structure for the heat generated from these circuit devices. In addition, the production cost tends to be raised due to use of the relatively expensive Si substrate 121 or glass substrate 131.
It is therefore an object of the present invention to provide a high frequency module device in which a high precision passive elements or a high density wiring layer is formed on a base substrate formed of inexpensive organic resin to improve the function, as well as to reduce the thickness and size and to lower the production cost. It is another object of the present invention to provide a method for the preparation of the a high frequency module device.
The high frequency module device according to the present invention includes a base substrate and a high frequency device layer deposited on this base substrate. The base substrate is made up of a core substrate formed of an organic material exhibiting thermal resistance and high frequency characteristics, and a patterned wiring layer formed on its first major surface. The uppermost layer is flattened out to form a high frequency device layer forming surface. The high frequency device layer, formed on the high frequency device layer forming surface of the base substrate by a thin film forming technique or a thick film forming technique, includes intra-layer passive elements, made up of a resistor, a capacitor or a patterned wiring, supplied with power or signals from the side base substrate through a dielectric insulating layer.
With the high free module device of the present invention, the high frequency device layer is directly formed, by the a thin film forming technique or by the thick film forming technique, on the high frequency device layer forming surface of the base substrate, exhibiting insulating properties and presenting a high precision flattened surface, so that passive elements or wiring layers of high precision and optimum high frequency characteristics may be formed within the bulk of the high frequency device layer. The overall cost of the high frequency device layer may be diminished because the base substrate is formed at a low cost on the core substrate of an inexpensive material in the same way as the conventional multi-layer substrate process. In the high frequency module device, in which the wiring for the power source or the grounding or the wiring of the control system is built in the base substrate and a high frequency signal circuit is formed in the high frequency device layer, electrical isolation may be achieved to suppress electrical interference to improve characteristics. With the high frequency module device, in which a power source of a sufficient area and the grounding wiring may be provided on the base substrate, power source supply with high regulation can be achieved.
The present invention also provides a method for the preparation of a high frequency module device comprised of a base substrate forming step and a high frequency device layer forming step. The base substrate forming step includes a first step of forming a core substrate from an organic material exhibiting thermal resistance and high frequency characteristics, a second step of forming a multi-layer wiring pattern layer on the first major surface of the core substrate and a third step of flattening out the uppermost layer to form a high frequency device layer forming surface. The high frequency device layer forming step includes a step of forming intra-layer passive elements by forming multiple layers comprised of a resistor, a capacitor or a wiring pattern supplied with power or signals from the side base substrate by a thin or thick film forming technique.
With the method for the preparation of the high frequency module device, according to the present invention, a high frequency device layer is directly formed by a thin or thick film forming technique on a high frequency device layer forming surface, designed as a high precision insulating planar surface, to provide a thin type high precision high frequency module device having high precision passive elements of optimum high frequency characteristics in the layers of the high frequency device layer. With the present method for the preparation of the high frequency module device, the wiring for the power source or the grounding or the wiring for the control system are provided on the base substrate, while a high frequency signal circuit is provided on the high frequency device layer, whereby the base substrate and the high frequency device layer are electrically separated from each other to suppress electrical interference to improve the characteristics of the high frequency module device. With the present method for the preparation of the high frequency module device, a high frequency module device may be produced in which the power source with a sufficient area for the base substrate and the grounding wiring may be formed in the base substrate to assure power supply with high regulation properties.
According to the present invention, the major surface of the core substrate formed of an insulating inexpensive organic material is flattened out to high precision to form a high frequency device layer forming surface, on which a high frequency device layer formed by a thin or thick film forming technique is directly formed to produce passive elements of high precision exhibiting superior high frequency characteristics by a simplified process. According to the present invention, in which the base substrate may be formed at a low cost by forming a multi-layer wiring layer on the core substrate of an inexpensive material by a process similar to the conventional multi-layer substrate process, a high frequency module device may be produced which is reduced in overall cost. With the present method for the preparation of the high frequency module device, the wiring for the power source or the grounding and the wiring for the control system are provided on the base substrate, while a high frequency signal circuit is provided on the high frequency device layer, whereby the base substrate and the high frequency device layer may be electrically isolated from each other to suppress electrical interference to improve the characteristics of the high frequency module device. According to the present invention, a high frequency module device may be produced in which the power source with a sufficient area for the base substrate and the grounding wiring may be formed in the base substrate to assure power supply with high regulation properties.